First Read is a morning briefing from Meet the Press and the NBC Political Unit on the day's most important political stories and why they matter.

Brexit and how it impacts American politics

As Britain goes to the polls to decide this question posed by The Clash -- Should I stay or should I go? -- it’s worth pointing out that the referendum on whether to remain in the European Union has a political angle here in the United States. After all, President Obama traveled to Britain two months ago to make the case for the country to stay in the EU. “The United States wants a strong United Kingdom as a partner. And the United Kingdom is at its best when it's helping to lead a strong Europe. It leverages UK power to be part of the European Union,” he said in London on April 22. Then there’s the 2016 presidential race: Donald Trump personally supports Brexit. "I would personally be more inclined to leave, for a lot of reasons like having a lot less bureaucracy," he told The Sunday Times, per Reuters. "But I am not a British citizen. This is just my opinion." Hillary Clinton, meanwhile, is on Team Remain. “Hillary Clinton believes that transatlantic cooperation is essential, and that cooperation is strongest when Europe is united,” her campaign said in a statement to a British paper. And, of course, there’s the angle how the Trump phenomenon helps explain the Brexit vote, given its focus on immigration and Making England Great Again. Don’t get us wrong: Today’s vote, first and foremost, is about Britain, the EU, and the global economy. But some American political actors have a stake in the game, too.

How the 'Brexit' vote could impact the US: Retirement, election, more2:16

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Scotland, here we come

And as Britain is votes on whether to exit the European Union, Donald Trump is, well, heading to Scotland. “In his first international trip since becoming the presumptive Republican nominee, Trump plans to check on a pair of his championship golf resorts. Some Republicans worry that the billionaire's attention is divided between his businesses and his campaign,” the AP writes. “‘I'm not sure what the purpose of the trip is,’ said Sen. John Thune, R-S.D., who added that he hopes Trump ‘would get back here quickly.’ Trump's son, Eric, who oversaw the two-year, more than $300 million renovation at the Trump Turnberry golf course, dismissed those concerns, saying ‘the eyes of the world’ will be on his father during a two-day stay in Scotland that begins Friday.”

Revolt in the House

Here on the other side of the pond, the top political story was yesterday’s sit-in revolt by House Democrats. NBC News: “A revolt in the House of Representatives turned raucous overnight, with protesting Democrats shouting down Speaker Paul Ryan's attempts to restore order during a gun-control protest that stretched into its 20th hour. Earlier, Republicans branded the move as a publicity stunt before summarily adjourning the chamber until after the Fourth of July. The stunning and unruly scenes were broadcast live to the world from Democrats' cellphones, feeds which were picked up by C-SPAN after Republicans shut down the network's cameras. Democrats took over the floor of the House at 11:25 a.m. ET Wednesday, demanding Republican leadership schedule votes on bills about universal background checks and blocking gun sales to those on no-fly lists. At 7:15 a.m. ET Thursday, a handful remained on the House floor.”

'Democratic revolution': Gun control sit-in on House floor rolls on3:30

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Sixteen days later -- and Sanders still hasn’t conceded

A reminder: It’s been 16 days since Hillary Clinton became her party’s presumptive presidential nominee, but Bernie Sanders still hasn’t conceded the race (nor has he endorsed Clinton). By contrast, Clinton officially conceded four days after Barack Obama became the presumptive nominee in 2008. We’re pointing this out, because Sanders yesterday -- for the first time -- acknowledged he won’t be the Dem nominee. “It doesn’t appear that I’m going to be the nominee,” he told C-SPAN, per NBC’s Danny Freeman. But he’s still giving a speech in New York tonight (entitled “Where We Go From Here”) that WON’T be a concession speech, Freeman and NBC’s Alex Seitz-Wald report. And then on Friday, he holds a “Future To Believe In” rally in Syracuse, NY featuring congressional candidate Eric Kingson. So the Sanders campaign still … goes … on.

Veepstakes Watch

POLITICO writes that Kaine has risen to the top of Clinton’s list, although the process is muddled by uncertainty about Trump’s nomination and his possible VP picks… Elizabeth Warren will campaign with Clinton in Ohio… The Boston Globe lays out the arguments for and against Warren… House Democrats are rallying around one of their own, Xavier Becerra, The Hill writes... On the GOP side: Ben Carson told Newsmax that Trump won’t make “a political pick”… Rick Scott’s approval rating is 43 percent to 46 percent in the latest Quinnipiac poll of Florida… Chris Christie says he’s “absolutely convinced” Trump will win… And John Thune isn’t thrilled with Donald Trump’s trip to Scotland, saying “I'm not sure what the purpose of the trip is.”

On the trail

Both Hillary Clinton and Donald Trump have no campaign events today. Don’t forget to check out the political unit’s rolling minute-to-minute coverage of all the latest 2016 developments at the On the Trail liveblog at NBCNews.com.